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From: Gerd Knorr <kraxel@bytesex.org>
Message-ID: <20031208095906.GB22878@bytesex.org>
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Subject: [uml-devel] Re: Workaround for bug #851759 -  SuSE YAST in textmode does not work
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Date: Mon, 8 Dec 2003 10:59:06 +0100
To: roland <for_spam@gmx.de>
Cc: user-mode-linux-devel@lists.sourceforge.net, uml-user <user-mode-linux-user@lists.sourceforge.net>

> "list systemProbe = SCR:Read(.probe.system);"

Oh, that one.  Didn't know yast triggeres this too.  That is actually
a bug in the uml kernel (there should be a mail in the -devel archive
...).  One if the things the hardware probes does is to check whenever
it runs within vmware or not, and that test hangs (source code below).

Known workarounds:
  * boot with "hwprobe=-sys" (that will make the hardware detect
    skip the critical test), or
  * don't use skas mode (it hangs in skas mode only for some
    musterious reason), or
  * just do something else in another terminal, that will unblock
    it too (scheduler bug in the uml kernel?).

> btw: what would be a better solution: asking the suse people to make
> yast "uml-aware" or fixing those things inside uml?

IMHO this one is a UML kernel bug.

  Gerd

==============================[ cut here ]==============================
#define _GNU_SOURCE		/* we want memmem() */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>

#include <sys/types.h>
#include <sys/wait.h>

void sigsegv_handler(int signum) { exit(77); }

int chk_vmware(void)
{
  static int is_vmware = -1;
  int child, status;

  /* do the check only once */
  if(is_vmware < 0) {

    child = fork();

    if(child == 0) {
      signal(SIGSEGV, sigsegv_handler);

      asm(
        "push %ebx\n"
        "\tpush %edx\n"
        "\tpush %eax\n"
        "\tpush %ecx\n"
        "\tmov $0x564d5868,%eax\n"
        "\tmov $0xa,%ecx\n"
        "\tmov $0x5658,%edx\n"
        "\tin (%dx),%eax\n"
        "\tpop %ecx\n"
        "\tpop %eax\n"
        "\tpop %edx\n"
        "\tpop %ebx\n"
      );

      _exit(66);
    }
    else {
      if(waitpid(child, &status, 0) == child) {
        status = WEXITSTATUS(status);
        if(status == 66) is_vmware = 1;
        if(status == 77) is_vmware = 0;
      }
    }
  }
  return is_vmware;
}

int main(int argc, char *argv[])
{
	int rc;

	fprintf(stderr, "check for vmware... ");
	rc = chk_vmware();
	fprintf(stderr, "%s\n", rc ? "yes" : "no");
	return rc;
}


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